Field of the Invention
The present invention relates to a gelled fluoride resin fine particle dispersion for use as a coating, to a method of production thereof, and to a method using this gelled fluoride resin fine particle dispersion to protect an alkaline inorganic hardened body.
Additionally, in detail, the present invention relates to a gelled fluoride resin fine particle dispersion which is coated onto inorganic building materials which comprise, in particular, an alkaline inorganic hardened body such as a concrete, mortar, and which excels in its ability to prevent leaching of the alkaline substance, and, besides which, is of a specific composition forming a coating which is excellent with respect to its weatherability, water resistance, and to its alkaline resistance and dirt picking resistance. The present invention further relates to a method of production of this gelled fluoride resin fine particle dispersion and to a method, using the same, for protecting an alkaline inorganic hardened body.
In the construction field, a coating process is applied on the surfaces of such alkaline inorganic hardened bodies as concrete, wall materials, roof materials or the like. The purpose of the coating is, principally, to render the substrate waterproof, weatherproof and resistant to chemicals. Additionally, this coating is carried out considering to the aspects of both protection and esthetic appeal.
In the construction field, an aqueous, organic polymer base coating is frequently used because it offers an advantage in that the coating process is easy apply.
As these type of organic polymer base coatings, acrylic polymer or acrylic styrene copolymers have been greatly in demand and are widely used.
However, recently, a life span for a coating material which is applied on the external surface of a structure, has become longer in the market; at a minimum, a 10 year, and preferably, a semipermanent life.
When the aforementioned aqueous polymers of acrylic type polymer or acrylic styrene copolymer types are used as a top coat, recoating is necessary again within a short time. In consideration of the aforementioned demand, the weatherability of this acrylic polymer or acrylic styrene copolymer type is insufficient.
On the other hand, an organic fluoro-olefin copolymer is also available for use. This fluoro-olefin copolymer is well-known as a binder to achieve excellent weatherability and chemical resistance. An organic solvent based fluoro-olefin copolymer is on the market.
However, because this fluoro-olefin binder contain organic solvents in high quantities it presents social problem as a fire hazard and harmful pollutant.
In contrast, the manufacture of a coating material that uses an aqueous dispersion of a fluoro-olefin polymer such as polytetrafluoroethylene, polyvinylidene fluoride or polyhexafluoropropylene has been disclosed. However, this kind of coating, which uses this type of aqueous dispersion, requires high temperature heating for film forming. For example, in spite of a low molecular weight, such that the intrinsic viscosity (.eta.) is 0.1.about.0.5, heating at high temperature of 180.degree..about.230.degree. C. is still necessary for the aqueous dispersion using a copolymer of vinylidene fluoride and hexafluoropropylene disclosed in Japanese Patent Application, laid open number SHO 57-38845.
To carry out such high temperature heating at a construction site or with the forced drying equipment within a factory is practically impossible. Accordingly, it has not been possible, using the aforementioned aqueous dispersion, to manufacture a coating for industrial utilization that relies on relatively low temperature forced drying, nor to produce a coating for use in the construction field that must form a paint film at ordinary temperatures.
Additionally, because fluoro-olefin monomers are expensive raw materials, the aqueous dispersion disclosed in the above Japanese Patent Application, laid open number SHO 57-38845, which uses a copolymer solely comprising those fluoro-olefin monomers, is not satisfactory from an economic standpoint.
However, in Japanese Patent Application, laid open number SHO 61-261367, an emulsion copolymer based resin composition has disclosed for use as a coating to resolve the above various problems. This copolymer is composed from fluoro-olefin, alkyl vinyl ether and carboxylic acid vinyl ester. This resin composition can be applicable for use in protecting an alkaline inorganic hardened body. However, this resin composition is not satisfactory with respect to its adherence to the substrate, pigment dispersibility, nor to its dirt picking resistance. Additionally, when polymerization is carried out under acidic or basic conditions for the vinyl ether monomer, the vinyl ether monomer itself breaks down, and side reactions occur. For this reason, a disadvantage is presented in that reaction will only take place within a limited pH range, specifically around pH 4.about.8. Thus, in the art up to now, it was necessary to add a large quantity of buffer to adjust pH. As a result, a fundamental problem exists in that, in association with water, the ability of coating film obtained is not sufficiently waterproof, alkaline resistant, etc.
Additionally, in Japanese Patent Application, laid open number HEI 2-240154 and Japanese Patent Application, laid open number HEI 2-240155, a fluoro-olefin copolymer aqueous dispersion produced from a combination of fluoro-olefin, olefin, vinyl ester and/or vinyl ether and a polymerizable unsaturated acid is disclosed as a coating that can be formed a film at ordinary temperatures.
However, the coatings disclosed in these applications is not satisfactory to prevent the leaching out of the alkaline substances breeding from the inorganic construction material. Furthermore, what is disclosed in these patent applications is merely an aqueous dispersion of a fluoro-resin that does not provide sufficient resistance to the effects caused by exposure to water and alkaline conditions over a long period.
In this manner, it has not been possible to block the leaching of the alkaline substance from the surface of an alkaline inorganic hardened body such as cement mortar, cement concrete, cement asbestos or calcium silicate board when these base materials encounter water or when hydration or further hardening occurs. Furthermore, an aqueous resin coating with a wide applicability has not been made available, which is superior with respect to its ability of weatherability, water resistance, and resistance to chemicals and dirt picking resistance over long time exposure to the elements.